1. Field of the Invention
The present invention relates to a conveying apparatus for plate-form members such as lead frames, substrates, etc. and more particularly to a claw structure that holds lead frames.
2. Prior Art
Conventionally, plate-form members, for instance, lead frames and substrates, are conveyed by plate-form member feeding mechanisms with both side edges of the plate-form members being guided by guide rails disposed so as to face each other in a parallel configuration. Such plate-form member conveying mechanisms have an upper claw and a lower claw that clamp or hold a plate-form member in between from above and below, a claw opening-and-closing mechanism that opens and closes the upper claw and lower claw (or moves the upper claw and lower claw toward and away from each other), and a claw feeding mechanism that causes the upper claw and lower claw to make a reciprocating motion in the conveying direction of the plate-form members. Accordingly, the plate-form members are conveyed one pitch at a time by a combination of the opening and closing movement of the upper and lower claws by the claw opening-and-closing mechanism and the reciprocating motion produced by the claw feeding mechanism in the conveying direction of the plate-form members.
The above system is disclosed in Japanese Patent Application Publication (Kokoku) No. 63-56122; and a similar system is disclosed in Japanese Patent No. 2835988 (that corresponds to Japanese Patent Application Publication No. 4-294550).
In the above prior art, the plate-form members are conveyed by being held from above and below by metal-made upper and lower claws. In such a structure, in cases where the plate-form members are large and heavy (e.g., plate-form members with a width of 40 mm, a length of 400 mm and a thickness of 2 mm), conveying errors have occurred at the rate of one member in four. In order to prevent such conveying errors, some improvements have been made by increasing the size of the clamping surfaces of the upper claw and lower claw or roughening these surfaces. Even in such cases, however, conveying errors have occurred at the rate of one member in 16. In cases where the clamping surfaces of the upper and lower claws are thus made of metal, there is little friction; as a result, the plate-form members slip.
Furthermore, in cases where die bonding or wire bonding is performed on the plate-form members, the plate-form members are heated by a heating block. There are cases in which the plate-form members are warped by this heat, so that the plate-form members cannot be held by the entire clamping surfaces of the upper and lower claws. In such cases as well, slipping occurs as a result of insufficient friction, resulting in conveying errors. Accordingly, in order to prevent conveying errors that involve warped plate-form members, a method is used so that the plate-form members are held by the upper and lower claws after warping has been eliminated by pressing the plate-form members with a warp-pressing member.
Therefore, the object of the present invention is to provide a conveying apparatus for plate-form members that conveys assuredly not only the plate-form members that are free of warping but also plate-form members that suffer from warping, and the alignment of the clamping surfaces of the upper claw and lower claw is easily accomplished, and the clamping plates is easily replaced.
The above object is accomplished by a unique structure of the present invention for a plate-form member conveying apparatus that includes an upper claw and a lower claw for clamping a plate-form member from above and below and conveying the plate-form member; and in the present invention, each of the upper claw and the lower claw is comprised of:
a clamping plate made of an elastic material and brought into contact with a surface of the plate-form member, and
a claw holding plate and a claw counter plate that are disposed so as to sandwich the clamping plate; and
the clamping plate and claw holding plate are detachably fastened by bolts to the claw counter plate.
In the above structure, the surfaces of the claw holding plate and the claw counter plate that face the leading edge of the plate-form member to be conveyed are formed so that such surfaces protrude toward the leading edge of the plate-form member from the clamping plate.
Furthermore, the elastic material can be a heat-resistant rubber.